The use of phosphorus-containing materials as flame retardants, corrosion inhibitors, adhesion promoters, and scale inhibitors is well known. Conventional phosphorus-containing additives are non-polymerizable and suffer from several drawbacks such as migration and leaching, leading to modification of adhesive, coating or film properties over time. Commercially available phosphorus-containing monomers, such as vinylphosphonic acid and ethylphosphonic acid monovinyl ester exhibit a reduced tendency for polymerization and give polymers with low molecular weight.
Commercially available alkylphosphates containing (meth)acrylic functionalities show reduced hydrolytic stability, as the phosphate or methacrylate ester bond can be cleaved in the presence of water. This reduces their storage stability and limits their applications.
(Meth)acrylic phosphonic acids and esters are known to be more hydrolytically stable than analogous phosphate acids and esters. These monomers are also known for their flame retardant and scale inhibiting activities.
For example, U.S. Pat. Nos. 3,030,347 and 2,934,555 teach dialkylphosphonoalkyl acrylate and methacrylate copolymers and methods for preparation. The compounds are used in leather or textile finishes for imparting flame retardancy.
U.S. Pat. No. 4,526,728 discusses phosphonate monomers for dyeing auxiliaries and scale inhibitors.
U.S. Published Application No. 2008/194730 discloses self-priming dental adhesive compositions containing phosphonic acid moieties. The invention alleges adhesion to enamel and/or dentin with a bond strength of at least 8 Mpa.
U.S. Pat. No. 4,029,679 discloses phosphonate monomers as a metal primer.
U.S. Pat. No. 6,740,173 discloses the use of phosphonate oligomer and phosphonate monomers (phosphonated methacrylates) in a composition for preventing metal corrosion with binder and metal reactive additives.
Bressy-Brondino, C. et al, Journal of Applied Polymer Science 2002, 83(11), 2277-2287, discloses blends of poly(vinylidene fluoride) and copolymers of methyl methacrylate and dimethyl 2-methylacryloyloxyethylphosphonate as a coating on steel.
U.S. Pat. No. 6,436,475 discloses a process for treating zinc, magnesium or aluminum wherein an organic compound with at least one phosphoric or phosphonic acid group is applied onto the metallic surface.
U.S. Pat. Nos. 4,738,870 and 4,658,003 disclose hydroxyphosphinylalkyl(meth)acrylates as adhesion promoting monomers.
There is still a need for hydrolytically stable phosphorus-containing monomers, which may be easily incorporated into resin based coatings, films and adhesives by simple blending of the phosphorus-containing monomer with at least one curing agent and curing resin. Surprisingly, more hydrolytically stable phosphonate-based compositions show also superior adhesion to metals.